This invention relates to polymeric blends of chlorosulfonated polyethylenes.
Chlorosulfonated polyethylenes are widely known and widely used commercially as elastomers in which the sulfonyl chloride moieties function as cross-linking or curing sites. They are resistant to ozone or oxygen degradation, and are generally solvent (oil) resistant. Chlorosulfonated polyethylenes are generally given the designation CSM in the industry.
It is known that the higher the chlorine content of a CSM the better the oil resistance, but as chlorine content increases, the glass transition temperature of the CSM increases thus making the polymer more brittle at low temperatures. In order to improve the mechanical properties and oil resistance, polyvinyl chloride has been blended with the CSM to reinforce the CSM elastomer and also to increase chlorine content of the overall blend (PVC has a chlorine content of 57 wt. % while CSM's have chlorine contents of 35-48 wt. % depending on the CSM).
However, blends of a CSM and PVC result in significantly degraded low temperature toughness, i.e., brittle point. And, in some cases, poor mechanical property retention results after submission in oil. For example, a CSM of 40 wt. % chlorine content blended with PVC had poor property retention after oil swell; and a CSM of 48 wt. % chlorine blended with PVC had poor low temperature toughness.
Chlorinated polyethylenes, because of the similar chemical composition, have very similar physical properties to CSM's of the same chlorine contents. The only important differences are the less versatile cure chemistry and the relatively higher residual crystallinity. Chlorinated polyethylenes are generally given the designation CPE in the industry.